(1) Field of the Invention
The present invention relates to a sorting apparatus which sorts packages by forwarding each of the packages which is being carried on a main conveyor to a corresponding one of the branch conveyors.
(2) Description of the Related Art
Conventionally, there are sorting apparatuses which sort packages which are being carried on their main conveyors such as roller conveyors according to the kinds, addresses, and the like of the respective packages.
For example, such sorting apparatuses include branch conveyors branching from their main conveyors, and forward packages which are being carried on their main conveyors to the branch conveyors for classifying the respective packages. The respective packages are sorted by the sorting apparatuses which perform such branching operations in this way.
In addition, it is desired that the sorting apparatuses can handle various kinds of packages. Therefore, the sorting apparatuses are required to securely forward such various kinds of packages to corresponding branch conveyors.
In view of this, there have been proposed techniques for securely forwarding such various kinds of packages to corresponding branch conveyors irrespective of the kinds of the products (for example, see Patent Reference: Japanese Unexamined Patent Application Publication No. 9-40174).
FIG. 7A is a diagram showing the outline of a conventional sorting apparatus.
As shown in FIG. 7A, a conventional sorting apparatus 100 includes a photoelectric sensor 102 on a path of a carriage conveyor 101 configured as a belt conveyor.
With this photoelectric sensor 102, it is possible to measure the length in the carriage direction of a package W which is being carried by the carriage conveyor 101.
In addition, the sorting apparatus 100 includes diverters 112 each of which is intended for forwarding packages to a corresponding one of branch conveyors 120. The details of the operation of each diverter 112 is changed according to the length in the carriage direction for the package W measured by the photo electric sensor 102.
FIG. 7B is a schematic plan view showing the operation starting timing of the diverter 112.
When the package W on the main conveyor 110 reaches a position which is along a side of a predetermined diverter 112 and is predetermined depending on the length in the carriage direction for the package W, the diverter 112 vibrates about an axis 116 inward at a predetermined speed.
The operation starting timing of the diverter 112 at this time varies according to the length in the carriage direction for the package W as shown in FIG. 7B.
In other words, as the length in the carriage direction for the package W becomes greater, the amount of forwarding the package W becomes greater. Here, the amount of forwarding corresponds to a forwarding distance between an entrance of the main conveyor 110 and a position at which the diverter 112 starts the operation for the package W.
As described above, the sorting apparatus 100 changes the operation according to the length in the carriage direction of a package. In this way, the sorting apparatus 100 can forward packages having different lengths to the corresponding branch conveyors 120.
Here, for example, even packages having approximately the same lengths may have characteristics different in terms of fall possibilities, damage possibilities, and the like.
Thus, a package may fall even in the case of changing the operation for forwarding the package to a corresponding branch conveyor (referred to as “branching operation” hereinafter) according to the length of the package by using the above-mentioned conventional technique.
As a matter of course, a certain amount of time is required for such branching operation. Thus, when plural packages, which are a current package and the next package, are sequentially supplied to the main conveyor, it is necessary to secure a proper interval between the current package and the next package which reaches a corresponding branch point immediately after the current package so as to prevent these packages from touching each other in the middle of the branching operation of the current package.
Accordingly, a conceivable countermeasure against this is to supply packages to a main conveyor spaced apart by a sufficiently long distance when the position in the branching operation is changed according to the length of the current package as in the conventional technique. This countermeasure makes it possible to prevent packages which are being carried sequentially from touching each other as described above.
However, the use of this countermeasure greatly decreases the number of sorted packages per unit time, thereby greatly decreasing the efficiency in sorting operations.